As an effort to obtain specimens that might be useful in the study of the presence on specific antigens in tumor types, anonymous tissue donations were accepted. We described a method to generate multitumor blocks without specific equipment. With these tissues, we characterized the distribution of several endothelial antigens: Claudin 5, PROX1, and VEGFR2 (KDR gene product). Also distribution of KBA62 and PNL 2 antigens in melanoma and other tumors was examined. We found VEGFR2 highly specific for endothelial tumors among mesenchymal cancers, but malignant mesotheliomas were found to be unique epithelial cancers strongly positive for VEGFR2. We also examined succinate dehydrogenase deficient gastrointestinal stromal tumors, in collaboration with NCI's pediatric GIST clinic.